Using live or neutral wire in AC household wiring as receiving antenna. Of course, this is possible only with high voltage capacitor inserted between the receiver antenna terminal and live or neutral wire. AC wiring antenna solution was mentioned as some type of last resort, when no other antenna can be installed due to space contraints. Ground conductor can be used as Earth ground.
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Old books recommend cold water pipe as ground connection, but I`m not sure whether this is good/practical/allowed any more. They also recommend "one good condenser" for antenna connection, not 2 in series. I guess people were braver then :) I decided to test this system myself. I made a small 2-transistor medium-wave AM receiver, with headphone output. To reduce main LC tank circuit loading, HF is taken from a capacitive divider of variable cap and 5 nF cap. Smaller voltage drop exists on larger capacitor due to its smaller capacitive reactance Xc=1/(2*pi*f*C). Voltage taken from main LC circuit decreases as higher frequencies are received: smaller capacitance of variable cap takes on more of capacitive divider voltage. This was deemed to be unimportant for fairly narrow range MW tuning. Received high frequency is demodulated at the base of first transistor and then amplified as low frequency in the first and second transistor. Calculated frequency range is approximately 700 kHz - 2800 kHz. To protect myself and my receiver, I decided to use two high voltage capacitors in series, antenna coil galvanically separated from remainder of circuit, and fuse. If high voltage spike is somehow able to penetrate through both 1 kV rated capacitors, it will blow open the fuse. Failing that, antenna coil (0. 3 mm diameter wire, 20 turns) will burn out, with no further damage done to receiver (or user). Hopefully. :) Several tests were...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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